Methods of operating one or more unmanned aerial vehicles within an airspace

ABSTRACT

In various embodiments, a safety system for an unmanned aerial vehicles (UAV) enable the safe operation of the UAV, alone or with other UAVs, within an airspace by initiating various actions based on the position of the UAV and/or one or more of the other UAVs relative to one or more flight zones and/or relative to other aircraft in the airspace.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/237,120, filed Oct. 5, 2015, the entiredisclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

In various embodiments, the present invention relates to the operationof unmanned aerial vehicles.

BACKGROUND

An unmanned aerial vehicle (UAV), commonly known as a drone or unmannedaerial system (UAS) and also referred to as a remotely piloted aircraft,is a flight vehicle without a human pilot aboard. Its path is controlledeither autonomously by onboard computers or by the remote control of apilot on the ground or in another vehicle. Drones have proliferated innumber as recognition of their widespread and diverse commercialpotential has increased. Numerous industries are embracing drones toimprove or streamline day-to-day operations. In addition, a rapidlygrowing hobbyist community has been inspired by the marvel of owningtechnology previously accessible only to governments, national agencies,and film producers with creative special effects departments.

With the growing number of active drones, and new applications beingimagined every day, legitimate concerns are being raised about risk tocivil aviation as well as to lives and property should a droneinadvertently leave its pilot's control. Such a drone can continueflying until it runs out of power or strikes an obstacle, while beingcompletely undetectable and invisible to manned aircraft andground-based air-traffic control management systems. Currently availabledrones are not designed to communicate with other fixed or airbornecivil aviation safety systems to avoid midair collisions. Thus, there isa need for improved systems and techniques for the safe operation ofdrones operated in airspace shared with other aircraft.

SUMMARY

Various embodiments of the present invention provide a platform thatfunctions as a “drone virtual radar system” (DVRS) that may beintegrated with existing drone designs and make these drones visible tocivil aviation in the event of a drone flight-control malfunction, orwhen the drone poses a potential hazard to manned aircraft. At the sametime, the DVRS offers drone operators additional layers of safetyassurance through real-time traffic monitoring and automatic triggeringof drone failsafe mechanisms. (The terms “UAV,” “UAS,” and “drone” areutilized interchangeably herein.)

In various embodiments, the DVRS and/or one or more components and/orfunctionalities thereof is integrated into a drone, for example, whenthe drone is assembled. In various embodiments, at least a portion ofthe DVRS is disposed within a stand-alone component that may beelectrically and mechanically connected to a drone after the drone hasbeen fabricated.

In various embodiments, the DVRS monitors, in real time, the state andvelocity of the drone that it is installed on. In addition, in variousembodiments the DVRS advantageously avoids civil-aviation safety-systemfrequency congestion by ensuring that any broadcasts by the drone occuronly when appropriate—i.e., when the drone presents a potential safetyhazard to civil aviation. Thus, if the drone is equipped with safetyoriented failsafe mechanisms, the DVRS may trigger one or more thereofif the drone leaves a predetermined flight zone (e.g., the boundsestablished by the drone operator and/or by government regulations).

If the drone is not equipped with any safety-oriented failsafemechanisms, or these mechanisms have failed to return the drone to itsapproved flight area (or disable the drone), the DVRS may, in variousembodiments, initiate a collision alert (e.g., a radio broadcast such asan automatic dependent surveillance broadcast and an activeinterrogation and monitoring of traffic collision avoidance system(TCAS) frequencies) to continuously alert civil aviation aircraft and/orground-based air traffic controllers to the drone state and velocity. Inthis manner, embodiments of the invention assure that the drone does notpose a safety hazard to civil aviation is by ensuring that the drone isfully visible to all civil aviation aircraft and ground-based airtraffic control stations to allow civil aviation aircraft to maneuveraway from the drone.

In various embodiments, the DVRS monitors in real time the state andvelocity of the drone that it is installed on while simultaneouslymonitoring in real time all civil aviation aircraft in close proximityto the drone. In some cases, such as drone operator error, or specialpermissions given to the drone operator to operate the drone in closeproximity to low flying civil aircraft, the DVRS may broadcast acollision alert when a civil aviation aircraft strays too close to thedrone. In this manner, the DVRS alerts civil aviation aircraft andground-based air traffic controllers to the drone state and velocityuntil the civil aviation aircraft has maneuvered away from the drone sothat the drone no longer poses a safety hazard to the civil aircraft.

In additional embodiments, the DVRS enables multiple drones in proximityto each other to interconnect in a wireless ad hoc network. One of thedrones in the network may be designated as the master node (or “masterdrone”), and in the event that a civil aircraft strays too close to thenetworked drones, the master drone may initiate a collision alert onbehalf of the entire network, thereby assuring that civil aviation radiofrequencies (e.g., the ADS-B and TCAS frequencies) are not saturatedwith multiple broadcasts from multiple drones in a tight formation.

In an aspect, embodiments of the invention feature a method of safelyoperating an unmanned aerial vehicle (UAV) within an airspace. Adesignated flight zone having an outer boundary is defined for the UAVwithin the airspace. A regulation-established flight zone having anouter boundary is defined for the UAV within the airspace. At least aportion of the outer boundary of the regulation-established flight zoneextends beyond at least a portion of the outer boundary of thedesignated flight zone. A position of the UAV relative to the designatedflight zone and relative to the regulation-established flight zone and aposition of the UAV relative to other aircraft in at least a portion ofthe airspace are monitored (e.g., simultaneously monitored). At leastone of (a) broadcasting a warning signal to the operator of the UAV, (b)initiating a failsafe protocol that removes the UAV from the airspace,or (c) broadcasting a collision alert from the UAV to at least oneaircraft in the airspace is performed based on at least one of (i) theposition of the UAV relative to the designated flight zone, (ii) theposition of the UAV relative to the regulation-established flight zone,or (iii) the position of the UAV relative to aircraft in the airspace.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The failsafe protocol may include,consist essentially of, or consist of one or more of automaticallyrouting the UAV back to an operator of the UAV or to another location,directing the UAV to descend and land, or activating a disablingmechanism for disabling the UAV. The disabling mechanism may include,consist essentially of, or consist of a kill switch and/or a parachute.The collision alert may be broadcast. The collision alert may include,consist essentially of, or consist of an automatic dependentsurveillance-broadcast (ADS-B) transmission and/or a traffic collisionavoidance system (TCAS) transmission. A range of the collision alert maybe controlled to be sufficient to be received only by aircraft within apredetermined distance from the UAV. Controlling the range of thecollision alert may include, consist essentially of, or consist oflimiting a power of the ADS-B transmission and/or a power of the TCAStransmission. The regulation-established flight zone may be definedbased at least in part on one or more rules. The one or more rules mayinclude, consist essentially of, or consist of one or more of a receivedsectional aeronautical chart, a received temporary flight restriction,or a government (e.g., Federal Aviation Administration) regulation. Atleast one of the rules may be received by the UAV when the UAV ispowered up and/or via a cellular network. The outer boundary of thedesignated flight zone may be updated at least once during operation ofthe UAV based at least in part on a revised flight restriction.

The failsafe protocol may be initiated when an aircraft enters thedesignated flight zone irrespective of the position of the UAV withinthe airspace. The failsafe protocol may be initiated when an aircraftenters the regulation-established flight zone irrespective of theposition of the UAV within the airspace. When an aircraft enters theregulation-established flight zone, the collision alert may be broadcastfrom the UAV at least to the aircraft irrespective of the position ofthe UAV within the airspace. When an aircraft enters the designatedflight zone, the collision alert may be broadcast from the UAV at leastto the aircraft irrespective of the position of the UAV within theairspace. The failsafe protocol may be initiated when the UAV leaves thedesignated flight zone irrespective of the position of any otheraircraft within the airspace. The failsafe protocol may be initiatedwhen the UAV leaves the regulation-established flight zone irrespectiveof the position of any other aircraft within the airspace. A disablingmechanism for disabling the UAV may be activated when the UAV leaves thedesignated flight zone irrespective of the position of any otheraircraft within the airspace. A disabling mechanism for disabling theUAV may be activated when the UAV leaves the regulation-establishedflight zone irrespective of the position of any other aircraft withinthe airspace. The disabling mechanism may include, consist essentiallyof, or consist of a kill switch and/or a parachute.

When a distance between the UAV and an aircraft within the airspacedecreases below a first threshold distance, the collision alert may bebroadcast from the UAV at least to the aircraft irrespective of theposition of the UAV within the airspace. When the distance between theUAV and the aircraft decreases below a second threshold distance smallerthan the first threshold distance, the failsafe protocol may beinitiated irrespective of the position of the UAV within the airspace.The collision alert may be broadcast from the UAV only if (i) a distancebetween the UAV and an aircraft within the airspace decreases below afirst threshold distance, or (ii) an aircraft enters theregulation-established flight zone, or (iii) the UAV leaves thedesignated flight zone. The collision alert may be broadcast from theUAV only if (i) a distance between the UAV and an aircraft within theairspace decreases below a first threshold distance, or (ii) an aircraftenters the regulation-established flight zone.

In another aspect, embodiments of the invention feature a method ofestablishing communication between a plurality of unmanned aerialvehicles (UAVs) operating within an airspace and an aircraft within theairspace. A wireless ad hoc network is established among the pluralityof UAVs. A first UAV is selected as a master node in the network. Acollision alert is broadcast from only the first UAV when a distancebetween the aircraft and any one of the UAVs decreases below a firstthreshold distance.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The collision alert may be broadcastfrom the first UAV when the distance between the aircraft and the firstUAV decreases below the first threshold distance. The collision alertmay be broadcast from the first UAV when the distance between theaircraft and a second UAV different from the first UAV decreases belowthe first threshold distance. UAVs other than the first UAV may bedesignated as slave nodes in the network. The collision alert mayinclude, consist essentially of, or consist of an automatic dependentsurveillance-broadcast (ADS-B) transmission and/or a traffic collisionavoidance system (TCAS) transmission. A range of the collision alert maybe controlled to be sufficient to be received only by the aircraft.Controlling the range of the collision alert may include, consistessentially of, or consist of limiting a power of the ADS-B transmissionand/or a power of the TCAS transmission. The first UAV may be selectedas the master node in the network based at least in part upon proximityof the first UAV to the aircraft (e.g., the first UAV may be the closestof the UAVs to the aircraft). The first UAV may be selected as themaster node in the network based at least in part upon the size of thefirst UAV, the transmitter power of the first UAV, and/or the powerreserve level of the first UAV. For example, the first UAV may be thelargest UAV in the network, the UAV in the network having the mosttransmitter power, and/or the UAV having the largest power reserve levelin the network. At least one UAV in the network other than the first UAVmay lack capability to broadcast the collision alert. For example, thetransmitter or transceiver utilized to broadcast the collision alert maybe absent, damaged, or otherwise nonfunctional. A second UAV differentfrom the first UAV may be selected as the master node in the network,and the first UAV may be designated as a slave node in the network. Theselection of the second UAV may be based at least in part on a change indistance between the aircraft and at least one UAV in the network (e.g.,the first UAV or the second UAV). For example, the second UAV may becomecloser to the aircraft than the first UAV based upon movement of thefirst UAV, the second UAV, and/or the aircraft. The collision alert maybe broadcast to the aircraft only with the second UAV after the secondUAV is selected as the master node in the network. Two or more, or evenall, of the UAVs in the network may be under control of a commonoperator. At least two of the UAVs in the network may be controlled bydifferent operators. Establishing the wireless ad hoc network among theplurality of UAVs may include, consist essentially of, or consist ofdetection, by at least one UAV, of one or more UAVs proximate the atleast one UAV, and initiation of a bi-directional wireless communicationlink between the at least one UAV and at least one of the one or moreUAVs.

In yet another aspect, embodiments of the invention feature a method ofsafely operating an unmanned aerial vehicle (UAV) within an airspace. Adesignated flight zone having an outer boundary is defined for the UAVwithin the airspace. A regulation-established flight zone having anouter boundary is defined for the UAV within the airspace. At leastportion of the outer boundary of the regulation-established flight zoneextends beyond at least a portion of the outer boundary of thedesignated flight zone. The outer boundary of the regulation-establishedflight zone is updated at least once during operation of the UAV.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The regulation-established flight zonemay be defined based at least in part on a received aeronautical chart(e.g., a received sectional aeronautical chart) and/or a received flightrestriction (e.g., a received temporary flight restriction). Theaeronautical chart and/or the flight restriction may be received by theUAV when the UAV is powered up and/or via a cellular network. The outerboundary of the regulation-established flight zone may be updated basedon a revised flight restriction. The outer boundary of the designatedflight zone may be updated based at least in part on the updated outerboundary of the regulation-established flight zone.

After updating the outer boundary of the regulation-established flightzone and/or after updating the outer boundary of theregulation-established flight zone, one or more of broadcasting awarning signal to the operator of the UAV, initiating a failsafeprotocol that removes the UAV from the airspace, or broadcasting acollision alert from the UAV may be performed based on (i) the positionof the UAV relative to the designated flight zone, and/or (ii) theposition of the UAV relative to the regulation-established flight zone.The failsafe protocol may include, consist essentially of, or consist ofone or more of automatically routing the UAV back to an operator of theUAV or to another location, directing the UAV to descend and land, oractivating a disabling mechanism for disabling the UAV. The disablingmechanism may include, consist essentially of, or consist of a killswitch and/or a parachute. The collision alert may be broadcast. Thecollision alert may include, consist essentially of, or consist of anautomatic dependent surveillance-broadcast (ADS-B) transmission and/or atraffic collision avoidance system (TCAS) transmission. A range of thecollision alert may be controlled to be sufficient to be received onlyby aircraft within a predetermined distance from the UAV. Controllingthe range of the collision alert may include, consist essentially of, orconsist of limiting a power of the ADS-B transmission and/or a power ofthe TCAS transmission.

In another aspect, embodiments of the invention feature a safety systemfor an unmanned aerial vehicle (UAV) operable within an airspace. Thesystem may include, consist essentially of, or consist of a computerprocessor, a memory, one or more sensors for sensing a position of theUAV, a velocity of the UAV, and/or a heading of the UAV, a hybridsurveillance module for monitoring radio transmissions from aircraft inproximity to the UAV, a plurality of radio transceivers each operatingon a different frequency, and a failsafe trigger module for operating adisabling mechanism configured to disable the UAV during operationthereof.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The one or more sensors may include,consist essentially of, or consist of a global positioning system unit,a camera (and/or other optical sensor such as a CCD array orphotodiode), and/or an inertial measurement unit (which may include,consist essentially of, or consist of, e.g., one or more accelerometers,one or more gyroscopes, and/or one or more magnetometers). The pluralityof radio transceivers may include an automatic dependentsurveillance-broadcast (ADS-B) transceiver (which may operate at afrequency of, e.g., approximately 1090 MHz), a second ADS-B transceiver(which may operate at a frequency of, e.g., approximately 978 MHz),and/or a traffic collision avoidance system (TCAS) transceiver (whichmay operate at a frequency of, e.g., approximately 1030 MHz). Theplurality of radio transceivers may include a cellular radiotransceiver, a VHF radio transceiver (which may operate at, e.g., one ormore frequencies between approximately 30 MHz and approximately 300MHz), a UHF radio transceiver (which may operate at, e.g., one or morefrequencies between approximately 300 MHz and approximately 3000 MHz),and/or a data link for communicating with other UAVs. The data link mayoperate at a frequency of approximately 2.4 GHz and/or at one or moreother cellular-communications frequencies. The disabling mechanism mayinclude, consist essentially of, or consist of a kill switch and/or aparachute. The disabling mechanism may be a component of the UAV, andthe system may merely interface with and operate the disablingmechanism. The disabling system may be a component of the safety system.

The computer processor may be configured to store, within the memory,(i) an outer boundary of a designated flight zone, and (ii) an outerboundary of a regulation-established flight zone. At least a portion ofthe outer boundary of the regulation-established flight zone may extendfarther from the UAV than at least a portion of the outer boundary ofthe designated flight zone. The computer processor may be configured todetermine, based at least in part on signals received from the one ormore sensors and/or the hybrid surveillance module, (i) a position ofthe UAV relative to the designated flight zone and to theregulation-established flight zone, and/or (ii) a position of the UAVrelative to other aircraft in at least a portion of the airspace. Thecomputer processor may be configured to, based on (i) the position ofthe UAV relative to the designated flight zone, (ii) the position of theUAV relative to the regulation-established flight zone, and/or (iii) theposition of the UAV relative to aircraft in the airspace, at least oneof: (a) broadcast a warning signal to the operator of the UAV, (b)initiate a failsafe protocol that removes the UAV from the airspace, or(c) broadcast a collision alert from the UAV to at least one aircraft inthe airspace. The computer processor may be configured to update theouter boundary of the designated flight zone and/or the outer boundaryof the regulation-established flight zone before, after, and/or duringoperation of the UAV. The computer processor may be configured to (i)update the outer boundary of the regulation-established flight zone, and(ii) based at least in part on the updated outer boundary of theregulation-established flight zone, update the outer boundary of thedesignated flight zone. The computer processor may be configured toupdate the outer boundary of the designated flight zone and/or the outerboundary of the regulation-established flight zone during operation ofthe UAV based on (i) a received aeronautical chart and/or (ii) areceived flight restriction. The computer processor may be configured to(i) form a wireless ad hoc network with one or more other UAVs, and (ii)only broadcast collision alerts to other aircraft within the airspace ifthe UAV is designated as the master node in the wireless ad hoc network.If the UAV is designated as a slave node in the wireless ad hoc network(or otherwise not designated as the master node in the wireless ad hocnetwork), the computer processor may be configured to not broadcastcollision alerts from the UAV, at least while the UAV is in the wirelessad hoc network, irrespective of the position of the UAV within theairspace and/or the position of another aircraft within the airspace.

These and other objects, along with advantages and features of thepresent invention herein disclosed, will become more apparent throughreference to the following description, the accompanying drawings, andthe claims. Furthermore, it is to be understood that the features of thevarious embodiments described herein are not mutually exclusive and mayexist in various combinations and permutations. As used herein, theterms “approximately” and “substantially” mean ±10%, and in someembodiments, ±5%. The term “consists essentially of” means excludingother materials that contribute to function, unless otherwise definedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1 is a schematic diagram of an airspace for drone operation inwhich multiple flight zones have been defined in accordance with variousembodiments of the present invention;

FIG. 2 is a schematic diagram of a drone initiating a failsafe protocolafter crossing the outer boundary of a designated flight zone inaccordance with various embodiments of the present invention;

FIG. 3 is a schematic diagram of a drone initiating a collision alertafter crossing the outer boundary of a regulation-established flightzone in accordance with various embodiments of the present invention;

FIG. 4 is a schematic diagram of a drone initiating a collision alertbased on the distance between the drone and another aircraft inaccordance with various embodiments of the present invention;

FIG. 5 is a schematic diagram of multiple drones forming a wireless adhoc network and initiating a collision alert from a master drone basedon the distance between one or more of the drones and another aircraftin accordance with various embodiments of the present invention; and

FIG. 6 is a block diagram of a drone virtual radar system in accordancewith various embodiments of the present invention.

DETAILED DESCRIPTION

In various embodiments, the DVRS enables the safe operation of the droneon which it is installed by monitoring the position of the dronerelative to one or more flight zones defined within the surroundingairspace and triggering various actions based at least on the drone'sposition. The DVRS may also monitor the position of other aircraftand/or drones within such boundaries and trigger actions based thereon.FIG. 1 depicts an exemplary embodiment of the invention in which a droneoperator (or simply “operator”) 100 is operating a drone 105 within anairspace 110. As shown, multiple different flight zones are definedwithin the airspace in accordance with embodiments of the presentinvention. In various embodiments, these flight zones include aregulation-established flight zone 115 and a designated flight zone 120.The regulation-established flight zone 115 and designated flight zone120 may have outer boundaries, as shown, and in typical embodiments thedesignated flight zone 120 will be disposed within theregulation-established flight zone 115; that is, the outer boundary ofthe designated flight zone 120 will be disposed entirely within (or, insome embodiments and/or portions of the boundary, substantiallycoextensive with) the regulation-established flight zone 115. In otherembodiments, the outer boundaries of the regulation-established flightzone 115 and designated flight zone 120 may overlap at one or morepoints, but at least a portion of the outer boundary of the designatedflight zone 120 is disposed within the regulation-established flightzone 115. The outer boundaries of the regulation-established flight zone115 and designated flight zone 120 may have any shape and may change orbe updated over time. In the embodiment depicted in FIG. 1, theregulation-established flight zone 115 and designated flight zone 120are substantially cylindrical and are therefore defined by radialdistances 125, 130 and heights (e.g., above ground level) 135, 140.

The regulation-established flight zone 115 may correspond to the portionof the airspace 110 in which the drone 105 is legally permitted tofunction. Thus, in various embodiments, the regulation-establishedflight zone 115 is defined based at least in part on, for example, oneor more regulations (e.g., government regulations) for the operation ofdrone 105 and which may depend at least in part on one or morecharacteristics of the drone 105 itself (e.g., size, capabilities,etc.). The regulations may also depend upon the particular location ofthe airspace 110 and, e.g., buildings or other structures within or nearthe airspace 110. For example, the regulation-established flight zone115 may be defined, at least in part, based on one or more regulationsissued by the Federal Aviation Administration (see, e.g.,https://www.faa.gov/regulations_policies/faa_regulations/). In variousembodiments, the regulation-established flight zone 115 may be defined,at least in part, based on one or more other rules, such as sectionalaeronautical charts of the airspace and/or one or more temporary flightrestrictions issued for the airspace, in addition to or instead of theone or more regulations. The rules defining the regulation-establishedflight zone 115 may be received by the drone 105 and/or operator 100before and/or during the flight of the drone 105; thus, the outerboundary of the regulation-established flight zone 115 may bedynamically altered during the flight of the drone 105. For example, oneor more of the rules may be received by the drone 105 over a localcellular communications network during or after the drone 105 is poweredup prior to flight.

The designated flight zone 120 may correspond to one or more portions ofthe airspace 110 designated for operation of the drone 105 by theoperator 100. For example, portions or the entirety of the outerboundary of the designated flight zone 120 may correspond to the boundsof the line of sight of the operator 100, the distance beyond which theoperator 100 determines may not allow safe operation of the drone 105,or one or more other factors. The outer boundaries of the designatedflight zone 120 and the regulation-established flight zone 115 may bedefined in terms of absolute position (e.g., latitudes and longitudes)and/or in terms of distance and height from the operator 100 or anotherpoint of reference. The outer boundary of the designated flight zone 120may be altered before and/or during the flight of the drone 105 by theoperator 100. For example, the operator 100 and/or the drone 105 mayreceive an updated or temporary flight restriction, and the outerboundary of the designated flight zone 120 may be altered to exclude oneor more portions of the airspace forbidden thereby. In embodiments inwhich the outer boundary of the regulation-established flight zone 115is updated during flight of the drone 105 based on a received rule(e.g., a received sectional aeronautical chart and/or a receivedtemporary flight restriction), the outer boundary of the designatedflight zone 120 may be updated based at least in part on the updatedouter boundary of the regulation-established flight zone 115. Forexample, the outer boundary (or a portion thereof) of the designatedflight zone 120 may be expanded or contracted to remain within therevised outer boundary of the regulation-established flight zone 115.

In accordance with embodiments of the invention, the position of thedrone 105 relative to the designated flight zone 120 and theregulation-established flight zone 115 (e.g., relative to the outerboundaries thereof) is monitored, and one or more actions may be takenin the event that the drone 105 strays from its intended portion of theairspace 110. For example, if the drone 105 crosses the outer boundaryof the designated flight zone 120, one or more actions may be taken,e.g., prior to the drone 105 reaching the outer boundary of theregulation-established flight zone 115. For example, the control systemof the drone 105 may broadcast a warning signal to the operator 100(and/or another recipient) and/or initiate one or more failsafeprotocols. In various embodiments, failsafe protocols may include,consist essentially of, or consist of automatically routing the drone105 back to the operator 100, directing the drone 105 to descend toground level and land, or activating one or more disabling mechanismsfor disabling the drone 105 and thus removing it from the airspace 110.For example, as shown in FIG. 2, the disabling mechanism may include,consist essentially of, or consist of a kill switch that stops thepropulsion system (e.g., one or more propellers and/or engines) of thedrone 105 and/or a parachute that slows the descent of the disableddrone 105 and hopefully limits any damage thereto resulting from such aforced landing.

In various embodiments of the invention, the drone 105 may not have suchfailsafe protocols and/or disabling mechanisms, or the failsafe protocoland/or disabling mechanism fails to operate and/or fails to return thedrone 105 to the designated flight zone 120 or remove the drone 105 fromthe airspace 110. In such embodiments, the drone 105 may broadcast acollision alert so that other aircraft 110 and/or ground-based airtraffic controllers are aware of the position, velocity, and/or headingof the drone 105 and thereby avoid approaching or colliding with drone105. For example, the collision alert may include, consist essentiallyof, or consist of an automatic dependent surveillance-broadcast (ADS-B)transmission and/or a traffic collision avoidance system (TCAS)transmission. As shown in FIG. 3, the collision alert may alert aircraft300 within airspace 110 to the presence of drone 105 and enable theaircraft 300 to avoid approaching or colliding therewith.

As known to those of skill in the art, TCAS is an aircraft collisionavoidance system designed to reduce the incidence of collisions betweenaircraft. TCAS monitors the airspace around an aircraft for otheraircraft equipped with a corresponding active transponder, independentof air traffic control, and warns pilots or operators of the presence ofother transponder-equipped aircraft that may present a threat of mid-aircollision. For example, see “Introduction to TCAS II Version 7.1,”published by the Federal Aviation Administration on Feb. 28, 2011, theentire disclosure of which is incorporated by reference herein. TCAStransponders and transceivers are conventional and may be procured orassembled without undue experimentation.

Similarly, ADS-B is a surveillance technology in which an aircraftdetermines its position via satellite navigation and periodicallybroadcasts it, thereby enabling tracking of the aircraft. The ADS-Binformation may be received by air traffic control ground stationsand/or by other aircraft. For example, see “Automatic DependentSurveillance-Broadcast (ADS-B) Out Performance Broadcast Requirements toSupport Air Traffic Control (ATC) Service,” 14 CFR Part 91, FederalAviation Administration, May 28, 2010, the entire disclosure of which isincorporated by reference herein. ABS-B transceivers and other equipmentare conventional and may be procured or assembled without undueexperimentation.

Various embodiments of the present invention thus avoid broadcastingcollision alerts from drone 105 unless and until the drone 105 hasbroached the outer boundary of a flight zone and/or one or more failsafeprotocols are absent or have failed to initiate. This advantageouslyavoids the flooding of various aviation frequencies with constanttransmissions from drone 105 even when drone 105 is not a potentialsafety hazard. In addition, the transmission range of the collisionalert may be controlled to be sufficient to be received only by aircraftand/or ground-based air traffic controllers within a predetermineddistance from the drone 105. For example, the power of the collisionalert transmission may be limited such that the alert is only receivablewithin the predetermined distance. In this manner, aviation frequenciesat distances farther from drone 105, e.g., where drone 105 is unlikelyto pose a safety hazard, are not flooded with collision alerts fromdrone 105.

In various embodiments of the invention, the drone 105 monitors thepositions of aircraft within the airspace 110 and initiates one or moreof various actions based on the position of an aircraft and/or thedistance between an aircraft and the drone 105 even if, for example, thedrone 105 is being otherwise safely operated within its designatedflight zone 120. For example, the drone 105 may monitor aviationfrequencies for, e.g., ADS-B and/or TCAS broadcasts from or about otheraircraft to determine their positions within the airspace 110. Upondetection of another aircraft, or when the aircraft approaches the drone105, one or more actions may be initiated. For example, a warning signalmay be broadcast to the operator 100 (and/or to another recipient), afailsafe protocol on drone 105 (e.g., a disabling mechanism) may beinitiated, and/or the drone 105 may broadcast a collision alert. Invarious embodiments, as shown in FIG. 4, the drone 105 initiates acollision broadcast when an aircraft 400 enters theregulation-established flight zone 115 irrespective of the position ofthe drone 105 within the airspace 110. In addition, in variousembodiments, the drone 105 may initiate a failsafe protocol when theaircraft 400 enters the designated flight zone 120 irrespective of theposition of the drone 105 within the airspace 110.

In various embodiments, one or more actions are initiated by the drone105 based on the relative positions of the drone 105 and the aircraft400 instead of or in addition to actions initiated based on the positionof the aircraft 400. For example, the drone 105 may broadcast acollision alert when the distance between the drone 105 and the aircraft400 decreases below a first threshold distance, even if the aircraft 400has not yet entered the designated flight zone 120 or theregulation-established flight zone 115. In addition or instead, thedrone 105 may initiate a failsafe protocol (e.g., a disabling mechanism)when the distance between the drone 105 and the aircraft 400 decreasesbelow a second threshold distance (which may be smaller than the firstthreshold distance), irrespective of the position of aircraft 400relative to the outer boundaries of the designated flight zone 120 orthe regulation-established flight zone 115.

In various embodiments of the invention, the drone 105 may monitor theposition of one or more other drones within airspace 110 (e.g., withinregulation-established flight zone and/or designated flight zone 120)and initiate one or more actions based on the positions of such dronesand/or the relative distance between drone 105 and one or more otherdrones. Such actions may be the same as those described above for drone105 relative to aircraft 300, 400, or one or more of the actions may bedifferent. For example, the drone 105 may communicate with one or moreother drones (e.g., on a non-civilian aviation frequency) to determinethe positions thereof, and the drone 105 may change course to avoidapproaching or colliding with such drones prior to or instead ofinitiating a failsafe protocol (e.g., a disabling mechanism or adirective to land).

Various embodiments of the present invention enable the safe operationof a group of drones within airspace 110, one or more of the dronesequipped with DVRS, in the event of an approach of another aircraftwithout each of the drones broadcasting its own collision alert, asmultiple such collision alerts may cause confusion or flood thebroadcast frequency. As shown in FIG. 5, drone 105 may be operatingwithin airspace 110 in proximity to one or more other drones 500 thatare each also under control of operator 100 or under the control ofanother operator. In the event of an aircraft 510 entering a portion ofthe airspace 110 (e.g., the regulation-established flight zone 115 orthe designated flight zone 120), communication may be establishedbetween only one of the drones (e.g., drone 105) and the aircraft 510 inorder to alert the aircraft 510 regarding the presence of all of thedrones 105, 500. For example, in various embodiments a wireless ad hocnetwork may be established among the drones 105, 500 (i.e., before orafter the approach of aircraft 510), and one of the drones (e.g., drone105) may be selected as the master node in the network. (While in theexemplary embodiments provided herein, drone 105 is designated as themaster node, one of the drones 500 may be the master node, and/or thedrone designated as the master node may change one or more times.) Drone105, and only drone 105, may then broadcast a collision alert based on,e.g., the position of the aircraft 510 within the airspace 110 (e.g.,relative to the regulation-established flight zone 115 or the designatedflight zone 120) and/or the relative position between the aircraft 510and one or more of the drones 105, 500. For example, each of the drones105, 500 may support a simple database for containing positionalinformation about the other drones, and in various embodiments, thisdatabase is actually used and updated only by the master drone.Positional information for each of the other (slave) drones may beexpressed and stored in terms of a drone's distance from aircraft withinthe airspace 110 and/or distance from the mater drone. The master drone105 may broadcast a collision alert if the distance between the aircraft510 and any of the drones 105, 500 decreases below a threshold distance.In this manner, all of the drones 105, 500 may be operated safely evenif one or more of the drones itself lacks the capability to broadcastthe collision alert. In addition, broadcasting collision alerts fromonly one drone in the network assures that aviation (e.g., ADS-B and/orTCAS) frequencies are not saturated with multiple broadcasts frommultiple drones in a tight formation.

In various embodiments, the wireless ad hoc network is established amongthe drones via detection, by at least one of the drones, of one or moreother drones in the proximity. For example, one or more drones may beequipped with cameras or other sensors capable of detecting the presenceof nearby drones, or the drones may broadcast short-range messages that,when received and responded to by another drone, indicate the proximityof the other drone. Once the other drone is detected, a bi-directionalwireless communication link may be initiated between the drones tonetwork the drones together. In various embodiments, drones communicatewith each other on non-aviation radio frequencies in order to avoidcongestion of the radio frequencies utilized by civil aviation (e.g.,1090 MHz, 978 MHz, and/or 1030 MHz). For example, each drone may sendmessages (or “pings”) to other drones within range at periodic intervals(e.g., each second or fraction of a second) on a frequency not typicallyutilized by civil aviation or having a range shorter than typical civilaviation frequencies. For example, the drone may communicate on a 2.4GHz frequency and/or another cellular communications frequency, whichtypically has a range limited to under two miles, in order to avoidcongestion of other radio frequencies. In this manner, communicationsfrom the drones over typical civil aviation frequencies (e.g., 1090 MHz,978 MHz, and/or 1030 MHz) that have much longer ranges (e.g., over 100miles) may be limited only to collision alerts if one or more of thedrones approaches or is approached by another aircraft.

Once the network is established, the drones may intercommunicate (e.g.,wirelessly) as nodes of the network. If all drones are within range ofeach other, they may send messages (which may be in the form of datapackets) over a fixed frequency using a wireless local area network orother suitable network arrangement in which each drone “multicasts”messages to all other drones in accordance with a communication protocolthat allocates network time among the drones. An advanced routingprotocol may be used to permit messages to reach all drones even thoughsome are out of radio range of the message-originating drone; each dronemay determine, for example by receiving position data from one or moredrones, which drones are within its range and propagate receivedmessages to neighboring drones in accordance with the protocol. Numerousschemes for routing messages across, for example, mesh networks areknown and may be employed herein; these include AODV, BATMAN, Babel,DNVR, DSDV, DSR, HWMP, TORA and the 802.11x standards. More generally,the network may be a wired or wireless local area network (LAN), a widearea network (WAN), an intranet, the Internet, the public telephoneinfrastructure, or some combination. It should be stressed that any ofnumerous modes of network communication can be utilized, e.g., directpeer-to-peer protocols, client-server architectures utilizing periodicpolling of each subsystem rather than explicit message transmission, ortoken-passing schemes.

Within the network of drones, the master drone (i.e., the master node ofthe network) may be selected based on any of various criteria. Forexample, a drone (e.g., drone 105) may be selected as the master droneif it is the closest drone to the aircraft 510. In other embodiments,the master drone may be selected based on, for example, the size of thedrone (e.g., the largest drone may be selected), the transmitter powerof the drone (e.g., the drone having the strongest radio transmitter maybe selected), and/or the power supply (e.g., remaining fuel and/orbattery power) of the drone (e.g., the drone having the largestremaining power supply may be selected). In other embodiments, themaster drone is selected substantially randomly or is one of the firstdrones to establish the network. As mentioned above, one or more of thedrones in the network may lack the capability to broadcast the collisionalert, and such drones would typically not be selected as the masterdrone.

In various embodiments, the drone designated as the master drone changesbased on any of a variety of different factors. For example, if thedistance between the master drone and aircraft 510 changes such thatanother drone in the network is closer to the aircraft 510, then the newcloser drone may be designated as the master drone and broadcast anynecessary collision alerts, and the former master drone may beredesignated as a slave node in the network. Similarly, if the powerreserves of the master drone are depleted to a threshold level, or ifone or more systems (e.g., a radio transmitter) of the master dronefail, another drone within the network may be designated as the masterdrone.

FIG. 6 is a block diagram illustrating basic components of a DVRS 600 inaccordance with embodiments of the present invention. As shown, the DVRS600 may include, consist essentially of, or consist of a system core 605and a transceiver bank 610. In various embodiments, the system core 605may communicate with the transceiver bank 610 via one or more hardwarecomponents such as field-programmable gate arrays (FPGAs). Thetransceiver bank 610 may include, consist essentially of, or consist ofone or more wideband agile transceivers that are configured to monitormultiple civil aviation navigational aids and civil air trafficcollision avoidance systems simultaneously. For example, as shown inFIG. 6, the transceiver bank 610 may feature one or more of transceivers615, 620, 625 for monitoring of and communication on ADS-B and TCASfrequencies, as well as one or more of a transceiver 630 for monitoringof and communication on cellular radio frequencies, a transceiver 635for monitoring of and communication on VHF radio frequencies, atransceiver 640 for monitoring of and communication on UHF radiofrequencies, and a transceiver 645 for monitoring of and communicationon one or more frequencies utilized by the DVRS 600 to communicate withother drones equipped with a DVRS and to form data links therewith. Forexample, the transceiver 645 may utilize one or more frequencies (e.g.,2.4 GHz or another cellular communications frequency) as described aboveto facilitate drone-to-drone communication and the establishment ofwireless ad hoc networks between drones.

Transceiver 630 may monitor and utilize any of a variety of cellularcommunications frequencies, which in various embodiments are based onthe geographic location in which the DVRS 600 is operating. For example,in the United States (and other locations in North America), suchfrequencies may range between approximately 800 MHz and approximately2.4 GHz (e.g., approximately 800 MHz, approximately 1.9 GHz, orapproximately 2.4 GHz); in Japan, such frequencies may range betweenapproximately 800 MHz and approximately 1.5 GHz (e.g., approximately 800MHz, approximately 1.5GHz, approximately 1.8 GHz, approximately 2.1 GHz,or approximately 2.5 GHz); in Europe, such frequencies may range betweenapproximately 380 MHz and 1.9 GHz (e.g., approximately 380 MHz,approximately 410 MHz, approximately 450 MHz, approximately 480 MHz,approximately 710 MHz, approximately 750 MHz, approximately 810 MHz,approximately 900 MHz, or approximately 1.9 GHz); in the Middle East,such frequencies may range between approximately 2.3 GHz andapproximately 2.6 GHz (e.g., approximately 2.3 GHz or approximately 2.6GHz); and in Australia, such frequencies may range between approximately700 MHz and approximately 2.4 GHz (e.g., approximately 700 MHz,approximately 800 MHz, approximately 1.9 GHz, or approximately 2.4 GHz).These frequencies are merely exemplary, and embodiments of the inventionmay utilize other frequencies.

The system core 605 typically features a computer processor (or simply“processor”) 650 and various other components operatively coupled to theprocessor 650. These components may include, consist essentially of, orconsist of, for example, a hybrid surveillance module 655, an inertialmeasurement unit (IMU) 660, a camera 665, a memory 670, a failsafetrigger module 675, and/or a flight data recorder 680 (which maycommunicate with or have a dedicated memory 685). The hybridsurveillance module 655 may control one or more of the transceiverswithin the transceiver bank 610, e.g., initiate monitoring of and/ortransmission (of, e.g., collision alerts) on specific frequenciestherewith. The IMU 660 is utilized for inertial navigation, to determinethe drone orientation, acceleration, velocity, and/or position. Forexample, the IMU 660 may include, consist essentially of, or consist of,for example, one or more conventional inertial navigation instrumentssuch as accelerometers and/or gyroscopes.

The system core 605 and/or the processor 650 may also interface with oneor more components that may be present on the drone independent of theDVRS 600. For example, as shown in FIG. 6, the system core 605 maycommunicate with and/or control one or more global positioning system(GPS) sensors 690 and/or one or more disabling mechanisms 695, e.g., akill switch and/or a parachute. A kill switch disables the drone'spropulsion system so that it falls back to earth. Typically, in order toavoid damage to the drone, the disabling mechanism 695 includes aparachute that is deployed when propulsion is disabled.

In other embodiments, such components are portions of the DVRS 600, asindicated by the dashed line in FIG. 6. The failsafe trigger module 675may control the disabling mechanism 695 based on, for example, theposition of the drone relative to one or more flight zones, the positionof one or more other aircraft or drones relative to one or more flightzones, and/or the position or one or more other aircraft or dronesrelative to the drone.

In various embodiments, the processor 650 receives and analyzes inputsfrom multiple sensors, e.g., hybrid surveillance module 655, GPS sensor690, IMU 660, and/or camera 665, to determine if the drone has strayedout of one or more flight zones in the surrounding airspace (as detailedabove) and therefore poses a threat to civil aviation aircraft, and/orif a civil aviation aircraft is getting too close to the drone while thedrone is still within its designated flight zone. Details (e.g., outerboundaries) of one or more flight zones may be stored within the memory670 and updated based on information received via the transceiver bank610, and the processor 650 may compare position information receivedfrom one or more sensors to such details to determine the position ofthe drone relative to the flight zone(s). The processor 650 may alsocompare flight zone information with position information of otherdrones and/or other aircraft in the airspace in order to initiatevarious actions, as detailed above.

In various embodiments, the processor 650 may execute algorithmsdisclosed (or similar to those disclosed) in “GPS/INS/Optic Flow DataFusion for Position and Velocity estimation,” International Conferenceon Unmanned Aircraft Systems (2013), the entire disclosure of which isincorporated by reference herein, to accurately determine the state andvelocity of the drone using multiple sensors (e.g., GPS information,optical flow information acquired using the camera, and inertialnavigation information acquired using the IMU). This information may beused to execute a decision algorithm; see, e.g., “UAS Safety: UnmannedAerial Collision Avoidance System,” IEEE Systems and InformationEngineering Design Symposium (2006), the entire disclosure of which isincorporated by reference herein, to trigger failsafe protocols such asa return to home autopilot override, parachute, or kill switch todisable the drone based on the drone position relative to one or moreflight zones, and/or to switch from passive (i.e., only monitoring) toactive (i.e., monitoring and transmitting, e.g., collision alerts)hybrid surveillance. In various embodiments, in the event that a civilaircraft is detected in close proximity to the drone, the processor 650may execute a combination of the algorithms described in “MovingObstacle Avoidance for Unmanned Aerial Vehicles,” 69th AmericanHelicopter Society Forum (2013) and “Sense and Avoid for Unmanned AerialVehicles Using ADS-B,” IEEE International Conference on Robotics andAutomation (2015), or Markov decision processes (see, e.g., “UnmannedAircraft Collision Avoidance Using Partially Observable Markov DecisionProcesses,” Lincoln Laboratory Project Report ATC-356 (2009)) to trackthe civil aircraft and predict if it is on a flight path that couldpotentially cause a conflict with the drone. The entire disclosures ofthe references cited in this paragraph are hereby incorporated byreference in their entireties.

In various embodiments, the processor 650 determines if the drone hasstrayed out of one or more flight zones, or if a civil-aviation aircraftis getting too close to the drone while the drone is still within one ormore flight zones based on one or more sensors (e.g., GPS 690, hybridsurveillance module 655, camera 665, and/or IMU 660). The GPS 690detects Global Positioning System satellite signals to determine theposition of the drone, while the agile transceivers of the transceiverblock 610 may be used to lock onto civil aviation navigational aids suchas radio beacons, e.g., VHF omnidirectional range (VOR) and/or distancemeasuring equipment (DME). The transceivers may also be utilized tocommunicate with the cellular network to triangulate the drone'sposition. In various embodiments, this allows the DVRS 600 to be moreresistant to GPS spoofing or drone position hijacking, and also enablesthe DVRS 600 to determine drone position in environments where receiptof GPS signals is intermittent or impossible. The hybrid surveillancemodule 655 passively monitors civil aviation activity in proximity tothe drone (e.g., over ADS-B and/or TCAS frequencies). If needed, theprocessor 650 utilizes the inputs from any one or more of these sensorsto switch from passive to active surveillance by configuring one or moreof the agile transceivers to begin broadcasting a collision alert. Forexample, the collision alert may include, consist essentially of, orconsist of the drone state (e.g., position) and velocity to be seen bycivil aviation aircraft and/or ground-based air-traffic controllers.

As detailed above, in the event that a civil aircraft strays too closeto a formation of drones (at least one of which is equipped with DVRS),the DVRS data link 645 may be used to coordinate with other DVRS (orsimilar) systems to designate a master drone that may initiate collisionalert and actively interrogate and monitor civil aviation (e.g., TCAS)frequencies to avoid civil-aviation system frequency overload.

The DVRS 600 may internally store a database representative of sectionalaeronautical information such as civil aviation navigational aidspecifications, and any flight restriction information in the region ofoperation in memory 670. This database may automatically update usingcellular radio frequency upon system power up, or in real time duringoperation.

In various embodiments, the DVRS internally records all the dataregarding the state and velocity of the drone that it is installed on inthe manner of a “black box” via the flight data recorder 680. The DVRS600 may also record all civil aviation traffic and/or all otherDVRS-equipped drone traffic in proximity to the drone. This informationmay thus be available to aviation safety and accident investigators inthe event of an incident involving the drone.

The terms “component,” “system,” “platform,” “module,” and the likerefer broadly to a computer-related entity or an entity related to anoperational machine with one or more specific functionalities. Suchentities can be hardware, a combination of hardware and software,software, or software in execution. For example, a component may be, butis not limited to being, a process running on a processor, a processor,an object, an executable, a thread of execution, a program, and/or acomputer. One or more components may reside within a process and/orthread of execution and a component may be localized on one computerand/or distributed between two or more computers. Also, these componentscan execute from various computer readable media having various datastructures stored thereon. The components may communicate via localand/or remote processes such as in accordance with a signal having oneor more data packets (e.g., data from one component interacting withanother component in a local system, distributed system, and/or across anetwork such as the Internet with other systems via the signal).

The processor 650 that executes commands and instructions may be ageneral purpose computer, but may utilize any of a wide variety of othertechnologies including a programmed microprocessor, micro-controller,peripheral integrated circuit element, a CSIC (customer-specificintegrated circuit), ASIC (application-specific integrated circuit), alogic circuit, a digital signal processor, a programmable logic device,such as an FPGA (field-programmable gate array), PLD (programmable logicdevice), PLA (programmable logic array), smart chip, or any other deviceor arrangement of devices that is capable of implementing thefunctionality described herein.

Various implementations of the systems and techniques described here canbe realized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various implementations can include implementation in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichmay be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms “machine-readable medium”“computer-readable medium” refers to any computer program product,apparatus and/or device (e.g., magnetic discs, optical disks, memory,etc.) used to provide machine instructions and/or data to a programmableprocessor, including a machine-readable medium that receives machineinstructions as a machine-readable signal. The term “machine-readablesignal” refers to any signal used to provide machine instructions and/ordata to a programmable processor.

The memory components described above may include computer storage mediain the form of volatile and/or nonvolatile memory such as read onlymemory (ROM) and random access memory (RAM). A basic input/output system(BIOS), containing the basic routines that help to transfer informationbetween elements, such as during start-up, is typically stored in ROM.RAM typically contains data and/or program modules that are immediatelyaccessible to and/or presently being operated on by processing unit. Thedata or program modules may include an operating system, applicationprograms, other program modules, and program data. The operating systemmay be or include a variety of operating systems such as MicrosoftWINDOWS operating system, the UNIX operating system, the LINUX operatingsystem, the Xenix operating system, the IBM AIX operating system, theHewlett Packard UX operating system, the Novell NETWARE operatingsystem, the Sun Microsystems SOLARIS operating system, the OS/2operating system, the BeOS operating system, the MACINTOSH operatingsystem, the APACHE operating system, an OPENSTEP operating system oranother operating system of platform.

Any suitable programming language may be used to implement without undueexperimentation the functionality described above. Illustratively, theprogramming language used may include assembly language, Ada, APL,Basic, C, C++, C*, COBOL, dBase, Forth, FORTRAN, Java, Modula-2, Pascal,Prolog, Python, REXX, and/or JavaScript for example. Further, it is notnecessary that a single type of instruction or programming language beutilized in conjunction with the operation of the system and method ofthe invention. Rather, any number of different programming languages maybe utilized as is necessary or desirable.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is:
 1. A method of establishing communication between aplurality of unmanned aerial vehicles (UAVs) operating within anairspace and an aircraft within the airspace, the method comprising:establishing a wireless ad hoc network among the plurality of UAVs, afirst UAV being selected as a master node in the network; andbroadcasting a collision alert from only the first UAV when a distancebetween the aircraft and any one of the UAVs decreases below a firstthreshold distance.
 2. The method of claim 1, wherein the collisionalert comprises at least one of: an automatic dependentsurveillance-broadcast (ADS-B) transmission; or a traffic collisionavoidance system (TCAS) transmission.
 3. The method of claim 2, furthercomprising controlling a range of the collision alert to be sufficientto be received only by the aircraft.
 4. The method of claim 3, whereincontrolling the range of the collision alert comprises limiting at leastone of a power of the ADS-B transmission or a power of the TCAStransmission.
 5. The method of claim 1, wherein the first UAV isselected as the master node in the network based at least in part uponproximity of the first UAV to the aircraft.
 6. The method of claim 1,wherein at least one UAV in the network other than the first UAV lackscapability to broadcast the collision alert.
 7. The method of claim 1,further comprising, based at least in part on a change in distancebetween the aircraft and at least one UAV in the network, selecting asecond UAV as the master node in the network and broadcasting thecollision alert to the aircraft only with the second UAV, the first UAVbeing designated as a slave node in the network.
 8. The method of claim1, wherein all of the UAVs in the network are under control of a commonoperator.
 9. The method of claim 1, wherein at least two of the UAVs inthe network are controlled by different operators.
 10. The method ofclaim 1, wherein establishing the wireless ad hoc network among theplurality of UAVs comprises: detection, by at least one UAV, of one ormore UAVs proximate the at least one UAV; and initiation of abi-directional wireless communication link between the at least one UAVand at least one of the one or more UAVs. 11.-20. (canceled)
 21. Themethod of claim 5, wherein the first UAV is selected as the master nodewhen the first UAV is the closest UAV to the aircraft.
 22. The method ofclaim 1, wherein the aircraft is not within the wireless ad hoc network.23. The method of claim 1, further comprising determining whether theaircraft is a second UAV or a manned aircraft.
 24. The method of claim1, wherein the first UAV is selected as the master node based on, atleast in part, a size of the first UAV.
 25. The method of claim 1,wherein the first UAV is selected as the master node based on, at leastin part, a transmission power of a radio transceiver of the first UAV.26. The method of claim 1, wherein the first UAV is selected as themaster node based on, at least in part, a remaining power supply of thefirst UAV.